No activity reported for 7 days, no location data, no alert received

When I login to check my teen's profile, NF says there is no activity for more than 7 days.  I know this to be false.  Also, my younger child's acct still shows some monitoring, so it seems as if the teen has disabled NF somehow.  I didn't receive any notifications about this though, and I don't know how to fix remotely.  Please advise!